Papermaker&#39;s fabric with adhesive resin encased yarns



3,313,645 PAPElfiiAKERS FABRIC WITH ADHESHVE ENCASED YARNS Joseph R. Wagner, Knoxville, Tenn, Tiber F. Matnska, Kentville, Nova Scotia, Canada, and Hugh E. Garrett, Markham, Qntario, Canada, assignors to Huyck Corporation, Stamford, Conn, a corporation of New York No Drawing. Filed Mar. 29, 1963, Ser. No. 269,136 2 Claims. (Cl. 11776) This invention relates generally to the treatment of greige fabrics to produce highly desirable paperrnakers fabrics which are stable under the particularly adverse conditions encountered in certain end uses, and to the product resulting from such treatment. More particularly, this invention relates to the treatment of woven belts or bands which in papermaking are known as forming fabrics, press fabrics and dryer fabrics, and are used to carry either a slurry of pulp or a wet web of paper through a papermaking machine.

Forming fabrics must be made of materials that are abrasive resistant, particularly in the cross-machine direction, and have extremely high tensile strength, at least in the machine direction, exhibiting low stretch properties, especially when wet. These fabrics must also be porous to permit the proper drainage of the paper stock. In addition they must not become flex fatigued. The fabrics must be stable dimensionally, so that they will not wrinkle, etc. on the Fourdrinier section.

Press fabrics must have high tensile strength to perform well, high dimensional stability so that they do not wrinkle or bulge on the press section, and be unaffected by moist conditions of operation. They must resist fiexural fatigue and fatigue as the result of the pressing action of the press rolls.

Dryer fabrics have particularly adverse conditions of use. They are exposed alternately to hot and wet material, and hot and dry material. To be effective, dryer fabrics must possess high tensile strength and substantial resistance to stretching, shrinking, abrasion, fatigue during fiexing, chemical action, and the like, whether wet or dry.

Papermakers fabrics have been made from wool, cotton, asbestos, synthetics and similar materials. In recent years the best results have been obtained with synthetic materials, such as nylon, polyester resins, and the like. However, synthetic fibers usually lack the degree of stiffness required in papermakers fabrics. Also greige fabrics of synthetic yarns, being normally smooth in surface, have a tendency to slip or shove and therefore lack dimensional stability. That is, synthetic yarns tend to move differentially, thereby producing interstices of non-uniform dimensions. Dimensional instability is disadvantageous because the space between yarns must be maintained substantially constant in order to have the fabrics function properly on a paper making machine.

Resin treatments of synthetic yarns have been known to enhance their properties, such as stiffness, abrasion resistance, etc. For instance, US. Patent 3,032,441, issued May 1, 1962, discloses the desirability of suitable treatment and other finishing steps to stabilize or otherwise condition fabric to meet demands which may be placed upon it. However, fibers derived from polyester resins have been resistant to all such treatments.

it is an object of this invention to provide non-metallic papermakers fabrics having improved dimensional stability, shove resistance, stiffness and like properties.

It is another object of this invention to provide a process for coating greige fabrics with a resin which adheres to the yarns thereof and encases the yarns with a resin coating, gluing the warp and filling fibers and yarns together at the yarn crossings, and thus producing highly desirable papermakers fabrics.

It is still another object of the present invention to provide a process for improving the dimensional stability, stiffness, abrasion resistance and other qualities of both fiat and endless open-weave paperrnakers fabrics made of synthetic material, including to a substantial extent, i.e., more than 10%, one or more of the group consisting of polyester fibers, silicate fibers, HT-l nylon fibers and polyolefin fibers formed from olefins having fewer than five carbon atoms.

Other objects will be apparent to those skilled in the art from reading the present disclosure.

Yarns is employed throughout the specification and in the appended claims in a broad sense and is intended to encompass strands formed from multi-filaments, monofilaments, staple fibers, etc. While the invention will be described in relation to fabrics formed at least in part of polyester fibers, it is to be understood that it is equally applicable to fabrics formed at least in part of silicate fibers, polyolefin fibers formed from olefins having fewer than 5 carbon atoms, HT-l nylon (which is Du Ponts trade name for a special high temperature nylon), and other synthetic fibers and naturally occurring animal and vegetable fibers that do not absorb or react with the treating resins but are subject to treatment in accordance With the invention.

Desirably the polyester fibers, silicate fibers, HT1 nylon fibers and polyolefin fibers constitute from 10 to 100 percent by weight of the fabric treated and preferably constitute from 20 to by weight thereof.

The objects of the present invention may be accomplished by treating a greige fabric with a resin which by adhesive power encases the yarns of which it is formed with a suitable coating and binds the warp and filling yarns together at the yarn crossings, and subsequently drying and curing the resin. After treatment the dimensional stability, stiffness, abrasion resistance, and like properties of the fabric are improved. Some of the resin treatments for synthetic fibers known to the art react with or partially dissolve certain synthetic fibers heretofore employed so that upon curing, the resin becomes part of the fiber. The resin of the present invention tends to encase the yarn and adhere to the fibers forming a coating thereon rather than becoming part of the fibers themselves.

The resin treatment of this invention is particularly applicable to polyester fibers. Thus it is especially useful in connection with the treatment of a fabric woven from a substantial amount of yarns of polyester fibrous material in multi-filament, mono-filament, staple fiber, or other suitable forms or combinations thereof.

Epoxy resins, acrylic resins and urethane resins are operative in the practice of this invention. An epoxy resin which has been found to be particularly useful in the practice of this invention is Resiweld Adhesive No. 4, which is a trademark of the H. B. Fuller Company, St. Paul, Minn, for a particular epoxy resin. Acrylic resins which have been found particularly useful in this invention include polyacrylic acid, sodium polyacrylate and other acrylic salts, esters, etc. The acrylic polymers are available commercially, for instance under the trade names Rhoplex AC-34 and Acrysol 2003 both sold by Rohm and Haas Company. Rhoplex AC-34 is an aqueous dispersion of acrylic polymers. The dispersion is a white, opaque liquid that produces a colorless, transparent film which possesses excellent permanence properties, durability, adhesion and the like. A polyurethane resin which has been found to be particularly useful in the practice of this invention is Unithane Resin 390T which is a trade name for polyurethane resins sold by the Thiokol Chemical Corporation, Trenton, New Jersey.

The acrylic resins, epoxy resins and urethane resins of this invention may be used individually as a sole treatment applied to fabrics to improve their characteristics. However, two or more of the resins may be used in combination to produce particular results. Also the special resins mentioned above may be used as an additional treatment of fabrics which have been previously treated with conventional resins of the prior art, in orderv to produce improved characteristics in the final fabric. For instance, the treatments disclosed in US. Patent 3,032,441 may be used as an initial treatment for fabric followed by treatment with the acrylic, epoxy or urethane resins of this invention.

The treatment process of US. Patent 3,032,441, comprises two stages of treatment. In the first stage, the endless fabric is treated with a phenolic-aldehyde resin, desirably one having a molar ratio of aldehyde to phenol of less than 1:1, such as a novolac resin. After drying and only partially curing the. phenolic-aldehyde resin absorbed during the first stage, the fabric is subjected to a second stage treatment employing an amino-aldehyde resin, such as a melamine-, urea-, or substituted ureaor substituted melamine-aldehyde resin. The amino-aldehyde resin desirably contains a suflicient molar excess of aldehyde to compensate for any molar deficiency of aldehyde in the phenolic-aldehyde resin employed in the first stage and to thereby contribute sufficient aldehyde to provide a ratio of aldehyde to phenol in excess of 1:1.

When used with the process of this invention the aminoaldehyde resin is then cured and the acrylic, epoxy or urethane resin is then applied as described above. The resin is dried and curing of the resins is carried out.

In the process of the present invention, the fabric to be treated is desirably tensioned in preferably both directions prior to treatment in order to establish predetermined lengthwise and widthwise dimensions with uniform yarn counts throughout each dimension and to square the fabric so that every transverse yarn thereof is at right angles to every longitudinal yarn. The critical treatments and finishing operations are carried out While the fabric is maintained under such tension.

It is a feature of the present invention that treatment with the acrylic, epoxy or polyurethane resin may be completed in one application of the resin. The application of resin to fabric may be carried out by an application roll, or by dipping the fabric into a solution of the resin, or by brushing or spraying. The application may be repeated, if desired, in order to increase the pick-up of the resin. If desired, the application may be carried out in more than one step with partial curing of the resin between the steps. The same or different resins may be applied in the various steps.

The total resin pick-up desirably ranges between about 5 and 40 percent by weight of the untreated fabric. Preferably, the total resin pick-up is between about 8 and 30 percent by weight of the untreated fabric.

After each resin has been applied, it is desirably heated to dry the resin in order that it not be removed from the material during subsequent treatments. After drying, the resultant fabric desirably is further heated to cure the resin. After drying and curing, the resin-containing fabric is further heated to heat set the fibers of which it is formed. Best results have been obtained at a heat setting temperature of about 425 F. The drying, curing and heat setting temperatures may be varied to suit the particular resins utilized.

The fabric after treatment is found to be heavier and stiffer than before treatment. There is a firmer bond between yarns than is obtainable with known treatments. The yarn diameters are increased due to the coating of resin which holds the yarns in fixed relation to each other. The interstices between the warp and weft yarns become smaller but should not be permitted to become plugged. It is important in applying the resin coating that excessive amounts of resin not be used which will cause the fabric to plug. The weave of the greige fabric should be such as to minimize the tendency to plug. Where resins tend to plug the fabric, it is desirable to blow the resin out of the interstices, for instance with compressed air. The superior treatment of the present invention is evidenced by the fact that drainage through the dryer fabric does not decrease as the fabric flexes and Wears.

The amount of pick-up by a spraying technique may be as great as the amount of pick-up by a dipping technique, provided that a sufiicient number of passes of the fabric through the spray apparatus are provided. The number of dipping steps, and also the concentration and the number of spraying steps, affect directly the amount of resin picked up.

A fabric treated with resin while under tension will initially shrink when put into use. A fabric treated with resin while extremely slack will stretch slightly when put into use. In cases where greater dimensional stability is desirable than is achieved by the special treatment in accordance with this invention, this may be achieved by employing the special tensioning technique of application Serial No. 240,435, filed Nov. 27, 1962, which was issued as Patent 3,192,599 on July 6, 1965. The optimum tension differs with each fabric and with conditions of treatment.

In order more clearly to disclose the nature of the present invention, specific examples of the practice of the invention are hereinafter given. While the examples represent exceptionally desirable forms of the invention, it should be understood that other yarns and resins than those to be specified, and other quantities and mixtures of the resins, may be utilized in accordance with the invention.

EXAMPLE 1 A test fabric was prepared having a weft comprising three plies of bright, high tenacity, multi-filament polyester yarns of approximately 1100 denier and made up of 250 filaments, the raw yarn having a twist of 12 turns per inch in the Z direction and the plied yarn having a twist of 5 turns per inch in the S direction. The Warp of the test fabric comprised three plies of bright, high tenacity nylon multi-filament yarns of approximately 520 denier and made up of 34 filaments, the raw yarn having a twist of 16 turns per inch in the Z direction and the plied yarn having a twist of 8 turns per inch in the S direction. The fabric had a weft count of 17 picks per inch, and a warp count of 25 ends per inch.

A resin treatment solution was prepared by dissolving three parts of Acrysol 2003 and one part of Rhoplex AC34 in four parts of water. The resin was rolled onto the fabric in two passes. After application of the resin, the fabric was dried at 250 F. The resin was then cured at 350 F.

After treatment the fabric was examined and found to have its yarns coated with resin that covered all of the yarns in their entirety and adhered tenaciously to them. The fabric was thicker and stifier after treatment than before, due to the increased diameter of the yarns as the result of their coating. This reduced the size of the interstices of the fabric. Accordingly, it would be desirable in some instances to use a coarser woven greige fabric to be subjected to the treatment, or to use a more dilute solution for the resin treatment.

EXAMPLE 2 Test fabric No. 3014 was prepared having 50 ends per inch of nine mil mono-filament nylon warp and 37 picks per inch of 4-ply Dacron filling. Resiweld Adhesive No. 4 was thinned with perchlorethylene in the ratio of 7 /2 quarts of Resiweld Adhesive No. 4 to 20 gallons of perchlorethylene. The resin was applied in two passes by an applicator roll which was kept revolving at maximum speed to keep the resin well mixed. The resin was dried at 250 F. and cured at 350 F. The fabric was then heat set at 425 F.

The product was tested to determine diagonal stability and resin adhesion. A sample was placed in boiling water for one-half hour and dried. A second sample was placed in boiling caustic with pH of 9 for onehalf hour, rinsed thoroughly, and dried. No resin loss was noted in either boiling Water or boiling caustic. The resultant product had a drainage rate of 28.57 gallons per minute and a diagonal stability of 7.

EXAMPLE 3 First step.-A phenol-formaldehyde resin condensate was used which may be produced by mixing phenol and a 37 percent aqueous solution of formaldehyde, water and barium hydroxide and heating the resulting mixture at above 150 F. with stirring. The reaction mixture is then concentrated to a thick resinous syrup by heating at reduced pressure. The thick resinous syrup is dissolved in 20% ethanol until the resulting solution then contains 5% by weight of resin solids.

Fabric No. 3102, having nylon warp yarns and polyester fiber-containing filling yarns, was passed through the resulting ethanolic phenol-formaldehyde resin solution, while under slight tension, so that it picked up about 100% by weight of solution. The fabric was air dried at a temperature of about 2l0-260 F. by being passed through a heating zone.

Second step.-A melamine-formaldehyde resin treatment solution was used which may be prepared by charging a reactor with 37% aqueous formaldehyde, adjusting the pH to about 8 with an aqueous solution of sodium hydroxide and adding melamine with stirring. The reaction mixture is heated to about 185 F. to dissolve all the melamine. A thick syrup results which solidifies upon cooling. The resulting melamine-formaldehyde resin is diluted with sufiicient water to provide a treatment solution containing about resin solids. To the solution may be added 5% by weight of urea and 1% by weight of hydrochloric acid.

The dried treated fabric of step 1Was passed continuously through the resulting melamine-formaldehyde treatment solution while still under slight tensioning so that about by weight of treatment solution was picked up by the fabric. The treated fabric, while still remaining under slight tension, was air dried at 210-260 F. by being passed through a heated zone.

Third step-The dried, treated fabric from step 2 was then treated with a solution of 3 parts of Resiweld Adhesive No. 4 and 64 parts of trichlorethylene to further stabilize the fabric. The treatment was carried out by passing the fabric through the resin solution while under slight tension. A stream of compressed air was used to blow excess resin solution from the interstices of the yarns. The fabric was then air dried at 210230 F. and further dried by heating to about 250F. by passing through a heating zone. After drying, the fabric was cured by heating it to about 350 F. by passing it through a heating zone. The fabric was then heat set by passing the fabric through a heating zone so as to raise the tempperature of the fabric to about 425 F.

After completion of the treatment the fabric was tested and found to have improved dimensional stability, abrasion resistance, shove resistance, stiffness and like properties.

EXAMPLES 4-28 The procedure of Example 2 was repeated varying the epoxy concentration, the solvent used, the application method and the fabric treated with the results contained in Table I below. Methylethylketone was used as a solvent in Examples 4-28 except in Examples 17-21 where trichloroethylene was used. The resin was applied either by an applicator roll or by a brush as indicated in Table I. In Examples 4-12 the fabric treated comprised three plies of bright high tenacity nylon multi-filament yarn made up of denier in the Warp direction and three plies of bright high tenacity nylon rnulti-filament yarn made up of 220 denier of filling yarns. The fabric was finished to approximately 49 /2 ends per inch and 35 picks per inch. In Examples 13-20, the warp was made up of two plies each of four filaments of 80 denier bright high tenacity yarn, the raw yarn having 25 turns per inch in the Z direction and the plied yarn having 16 turns per inch in the S direction. The filling yarns were made up of three plies each of 34 filaments of 70 denier polyester fibers, the raw yarn having 22 turns in the Z direction and the plied yarn having 13 turns in the S direction. The fabric was finished to 74 ends per inch and 69 picks per inch. Examples 21-28 had warps composed of 9 mil, type 5, mono-filament nylon yarns and filling yarns made up of 4 ply, 28 filaments, 140 denier polyester fiber, the raw yarn having 15 turns per inch in the Z direction and the plied yarn having 9 turns per inch in the S direction. The material was finished to 48 ends per inch and 33 picks per inch. The product after treatment was subjected to the following tests.

Samples of the fabric after treatment were subjected to tensile tests, abrasion tests and tests for measurement of diagonal stability. The tensile test was carried out on a sample one-half inch wide by six inches long. The sample was wetted by soaking in water for at least one hour. The sample was then inserted in an Instron measuring apparatus, and tension was applied, measured and recorded.

Abrasion tests were run on a Taber Abrader using H-18 abrasion wheels weighted with 250 g. The samples were run for 400 cycles while dry. The samples were then wetted for at least one hour, and then the machine direction and cross direction percent strength retained were determined by the tensile test above.

Diagonal stability was determined on samples one inch Wide and six inches long which were cut on the diagonal. The samples while in the dry condition were tested by the tensile test above. The degree of diagonal stability was determined by observing the initial portion of the stress-strain curve.

7 8 TABLE I MD CD Abrasion, Percent Epoxy Parts Application G/M Strength Retained Diagonal Example Resin, Solvent Method Drainage Stability, Parts Tensile Percent Tensile Percent Pounds Strength, Elonga- Strength, Elonga- MD CD Pounds tion Pounds tion 3 341. 6 11.3 163 25. 5 04. 70 13. 02 1 3 333.2 11.67 156 3 22.67 101. 50 14. 67 1 3 341. s 11. 70 149. 2 24. 77 100. 65 3. 33 3 3 344. 4 11. 53 136. 6 23. 23 102. 70 16. s 1 3 343. 6 11.60 169. 4 27. 63 04. 59 12. 00 2 3 345 11.33 105. 6 29. 7 100. 44 2. 30 1 3 351.4 13. 39 203 4 35.10 101.73 6.15 5 3 338.6 13. 62 204 2 37.6 102. 48 3.10 5 3 342.6 14.13 207 3 34.40 104.03 2.39 5 3 167 21.50 115 33.26 107.19 19.13 5 3 167. 3 20. 60 114. 4 33. 53 103. 30 24. 03 13 3 170. 6 23. 67 110. 6 33. 30 101. 90 10. 89 3 3 163. 4 21.53 115. 4 35. 00 100. 3b 17.33 5 3 167. 0 22. 07 108. 2 30. 16 100. 0 17. 00 17 3 168. 3 21. 37 111.3 30. 50 100. 72 17. 00 3 3 174. 3 25.13 112. 2 31. 43 98.12 14. 26 11 3 303. 5 14. 37 149. 7 47. 37 102. 03 0. 35 3 211.3 20. 63 150.4 41.00 105.52 13 63 1 3 210 21.17 150. 3 43. 00 96. 67 10 3 5 4 3 104.4 21.73 105.6 44.70 97. 74 10 23 3 104.4 24. 37 173.4 47.63 03. 26 16 32 s 3 100 25. 03 163. 4 41. 30 102.11 12 24 3 190 20 161.2 41.06 101.06 14.53 52 3 101.3 9 10 165.6 44.20 93. 23 0.65 12 3 100 4 24 30 171.4 47.07 33 24 16.05 31 1\lD-\lachinc Direction. (JD-Cross Maohinc Direction.

The terms and expressions which have been employed 2. A papermakers fabric according to claim 1 wherein are used as terms of description and not of limitation, 0 said yarns have an undercoating of a phenolic aldehyde and it is not intended in the use of such terms and exresin, a coating of an amino-aldehyde resin, and a top pressions, to exclude any equivalents of the features coating of said adhesive resin. shown and described or portions thereof, but it is recognized that various modifications are possible within the References cued by the Bummer scope of the invention claimed. In lieu of the specific 35 UNITED STATES PATENTS resins mentioned herein, it is possible to employ appro- 2,05O156 8/1936 Borghetty priate solutions of a variety of resins of the epoxy family 2,491,454 12/1949 Nuts 117 9g that are capable of forming a coating over the surfaces 2,374,069 2/1959 Gagarine et 117 133 8 X of the yarns forming the greige fabric subjected to the 2,903,021 9/1959 Holdan et a1 X treatment. Also, a polyurethane resin such as Unithane 2,943,634 8/1960 Furendal et a1. 390T resin, may be used in place of the Acrysol 2003, 2 955 9 1 10/19 0 Koner 117 13 and Rhoplex AC34 or Resiweld No. 4 in the examples. 2,977,665 4/1961 McElmth 117 7 X What defined 1S1 2,993,313 7/1951 Tischbein 117 -133.s X

1. An 1mproved paperrnakers fabric comprismg yarns 3,003,191 10/1961 Luth 117 126 X made from materials selected from the group consisting 3,024,216 3/1962 Smitmans et a1 X of polyester resin fibers, s1l1ceous fibers, polyam1de fibers, 3:032441 5/1962 Beaumont et 117 138 8 and polyolefin fibers, wherein said yarns have been coated 3,067,059 12/1962 Jannarem et aL X with an adhesive resin selected from the group consisting 3,228,790 1/1966 Sexsmith at al 117 138'8 of epoxy resins and acrylic resins, which firmly adheres 3,236,635 2/1966 Caldwell et a1. 117 138 8 t0 the surfaces 0f said yarns Witl'lOllt any substantial pene- 3 252 21 5 19 Christie et 1 117 13 tration thereof by said resin such that said yarns will be H caused to be joined together at their intersections and olHER REFERENCES the diameter and stiifness of said yarns will be increased, Chemical Week, vol. 88, No. 15, 1961 (pp. 9194, wherein said adhesive resin comprises between about 5 e1i d to 40% by weight of said fabric, said fabric having irn- T proved dimensional stability, abrasion resistance, and WHLIAM MARTII\ Primary Exammer' stiffness. R. HUSACK, Assistant Examiner. 

1. AN IMPROVED PAPERMAKER''S FABRIC COMPRISING YARNS MADE FROM MATERIALS SELECTED FROM THE GROUP CONSISTING OF POLYESTER RESIN FIBERS, SILICEOUS FIBERS, POLYAMIDE FIBERS, AND POLYOLEFIN FIBERS, WHEREIN SAID YARNS HAVE BEEN COATED WITH AN ADHESIVE RESIN SELECTED FROM THE GROUP CONSISTING OF EPOXY RESINS AND ACRYLIC RESINS, WHICH FIRMLY ADHERES TO THE SURFACES OF SAID YARNS WITHOUT ANY SUBSTANTIAL PENETRATION THEREOF BY SAID RESIN SUCH THAT SAID YARNS WILL BE CAUSED TO BE JOINED TOGETHER AT THEIR INTERSECTIONS AND THE DIAMETER AND STIFFNESS OF SAID YARNS WILL BE INCREASED, WHEREIN SAID ADHESIVE RESIN COMPRISES BETWEEN ABOUT 5 TO 40% BY WEIGHT OF SAID FABRIC, SAID FABRIC HAVING IMPROVED DIMENSIONAL STABILITY, ABRASION RESISTANCE, AND STIFFNESS. 